How can addiction destroy a nation?

In the drug legalization debate, there are many sides to come at it from. Societal costs, difficulty of enforcement, libertarianism, etc. But it is important to remember that addictive substances should also be feared for the distortions they can put onto economies. Consider this situation in Yemen with their national addiction, Qat.

Qat, a mild narcotic plant, is chewed daily in almost every part of the country and is an integral part of the culture here. It has become Yemen's addiction, requiring a steady supply to feed the nation's growing demand.
"The farmers here prefer growing qat to growing grapes," laments Mohammed. "Growing qat makes them more money, but growing it also uses up much more water."...
The situation is so critical that, out of the country's 15 aquifers, only two are being replenished. Some members of Yemen's government have floated the idea of moving the capital, as well as desalinating seawater on the coast and pumping it to Sana'a...
When asked if he knows his country will soon run out of water and what that means for future generations, he sighs.
"The farmers here -- we have no future -- we have to rely on God," says Mohammed. "We only have God's mercy to rely on."

Sometimes the costs on society of bad choices do not end with the individual. These bad choices can easily mushroom and draw thousands of others into a trap with no way out.